Effect of western drought on the water resources of Safford Valley, Arizona, 1940–1952

Abstract

Re cords of precipitation, runoff in the Gila River, ground‐water withdrawals for irrigation, and changes in ground‐water level in Safford Valley, Arizona, provide a basis for noting the effect of wet and dry periods on the hydrologic cycle. An unusually wet period 1940–1941, was followed by a period of drought, l942–1952. The irrigable area is limited by natural causes, the area irrigated with surface water is effectively limited by court decree, and less than 1000 acres are irrigated exclusively from wells. Thus relatively little expansion in this irrigated area has occurred during the period concerned to obscure the climatic effects, although cultivation has been more intensive in recent years and the water demand has been correspondingly larger. The wet period of above‐normal stream flow and ground‐water levels provided a cushion that delayed and reduced the effects of the drought. As the ground‐water‐storage in the valley is relatively small, however, withdrawals of ground water as a supplemental supply for irrigation eventually lowered water levels sufficiently to reduce well yields. The concentration of dissolved mineral matter increased in the remaining ground water, making it less desirable for irrigation use than previously.